With portable electric appliances such as VTR, vacuum cleaner and others being rendered compact, a battery for use as an electric power source therefor has been strongly desired to be made compact. As an electric power source for the above described types of portable electric appliances, a lead storage battery and a nickel-cadmium storage battery are mainly utilized.
The lead storage battery makes use of a battery case of synthetic resin having a plurality of, for example, three, cell chambers, and is of such a construction that polar plate groups are inserted into the respective cell chambers with cells being connected together by means of a connector means fluid-tightly passing through partition walls.
In the nickel-cadmium storage battery, an exemplary type is that a plurality of unitary cells armored in metallic vessels are combined together and are in turn inserted into a single vessel.
However, in the lead storage battery of the above described construction, there is a problem in that not only is it difficult to make the battery thin because of the partition walls separating the cell chambers, but also the manufacturing cost tends to become high because a complicated fabricating step is required wherein the polar plate groups are incorporated individually into the respective cell chambers in a battery case. Also, in the lead storage battery, while it is essential to apply an appropriate pressure, that is, a so-called group pressure to the polar plate groups in order to prevent active substances of an anode from being particulated and to prolong the lifetime of the battery, a problem arises wherein, since the group pressure differs from one cell to another, the cells are not uniform in lifetime. Moreover, in a sealed storage battery wherein the quantity of electrolyte is controlled, since the quantity of the electrolyte retained by a separator means varies when the group pressure differs from one cell to another, a disadvantage arises in that the capacity varies. Even in the nickel-cadmium storage battery, since the completely independent cells are combined, there is a problem in that wasteful spaces are many and the capacity efficiency for a battery is low.